Heating water at constant volume and pressure

In summary, the problem involves a rigid tank with a volume of 0.01m3 containing saturated water at 200°C and a quality of 0.4. The top of the tank has a pressure-regulating valve that maintains constant vapor pressure. The system is heated until all the liquid vaporizes, and the question is asking for the required head in kJ. To solve this, we can use the steam tables to calculate the total molar volume and mass of the water. We can assume that the temperature will remain constant as vapor continues to leave the system. The energy leaving with the vapor can be tracked by considering the change in internal energy.
  • #1
debussie
2
0
A rigid tank has a volume of 0.01m3. It initially contains saturated water at a temperature of 200°C and a quality of 0.4. The top of the tank contains a pressure-regulating valve that maintains the vapor at constant pressure. This system undergoes a process whereby it is heated until all the liquid vaporizes. How much head (in kJ) is required? You may assume that there is no pressure drop in the exit line.
 
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  • #2
Please could you provide your attempt at the solution.

Jared
 
  • #3
So far I have used the quality given, and the steam tables to calculate the total molar volume and total mass of the water:

Vm=(1-x)Vml+xVmv
m=V/Vm

I am assuming that the temperature of the system won't change because vapor will continue to leave as more vapor is created. I'm not sure where to go from here. Does Q=change in U? How do I keep track of the energy that is leaving with the vapor?
 

1. How does heating water at constant volume and pressure affect its temperature?

When heating water at constant volume and pressure, the temperature of the water will increase. This is because the volume and pressure remain constant, so the only way for the water to absorb the added heat energy is by increasing its temperature.

2. What is the purpose of heating water at constant volume and pressure?

Heating water at constant volume and pressure is often done in laboratory experiments to study the properties of water, such as its specific heat capacity and thermal expansion. It can also be used in industrial processes, such as steam generation in power plants.

3. How does the specific heat capacity of water affect heating at constant volume and pressure?

The specific heat capacity of water is the amount of heat energy required to raise the temperature of water by one degree Celsius. Since heating at constant volume and pressure involves adding heat energy, the specific heat capacity of water plays a crucial role in determining the temperature change of the water.

4. Can water be heated at constant volume and pressure in a closed system?

Yes, water can be heated at constant volume and pressure in a closed system. This means that the volume and pressure of the system remain constant, but heat energy can still be added to the water. This process is often used in thermodynamic calculations and experiments.

5. How does heating water at constant volume and pressure differ from heating it at constant pressure?

When heating water at constant volume and pressure, the volume of the water remains constant while the pressure remains constant. On the other hand, heating water at constant pressure allows the volume of the water to change as it absorbs heat energy. This can lead to different temperature changes and is often used in industrial processes.

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